Limited Energy Density Research Articles

Interlayer Confined Water Enabled Pseudocapacitive Sodium-Ion Storage in Nonaqueous Electrolyte.

Electrochemical capacitors have faced the limitations of low energy density for decades, owing to the low capacity of electric double-layer capacitance (EDLC)-type positive electrodes. In this work, we reveal the functions of interlayer confined water in iron vanadate (FeV3O8.7·nH2O) for sodium-ion storage in nonaqueous electrolyte. Using an electrochemical quartz crystal microbalance, in situ Raman, and ex situ X-ray diffraction and X-ray photoelectron spectroscopy, we demonstrate that both nonfaradaic (surficial EDLC) and faradaic (pseudocapacitance-dominated Na+ intercalation) processes are involved in the charge storages. The interlayer confined water is able to accelerate the fast Na+ intercalations and is highly stable (without the removal of water or co-intercalation of [Na-diglyme]+) in the nonaqueous environment. Furthermore, coupling the pseudocapacitive FeV3O8.7·nH2O with EDLC-type activated carbon (FeVO-AC) as the positive electrode brings comprehensive enhancements, displaying the enlarged compaction density of ∼2 times, specific capacity of ∼1.5 times, and volumetric capacity of ∼3 times compared to the AC electrode. Furthermore, the as-assembled hybrid sodium-ion capacitor, consisting of an FeVO-AC positive electrode and a mesocarbon microbeads negative electrode, shows a high energy density of 108 Wh kg-1 at 108 W kg-1 and 15.3 Wh kg-1 at 8.3 kW kg-1. Our results offer an emerging route for improving both specific and volumetric energy densities of electrochemical capacitors.

Optimization of Flow Channels in a PEM Fuel Cell Based on a Multiobjective Evaluation

Optimization of Flow Channels in a PEM Fuel Cell Based on a Multiobjective Evaluation

High-Performance Lithium Metal Batteries

The success of rechargeable lithium-ion batteries (LIBs) has brought evident convenience to human society, but state-of-the-art LIBs with a graphite anode are approaching their energy density limits. Li metal is considered the ultimate anode material due to its ultra-high theoretical specific capacity of 3860 mAh g-1, which is more than 10 times higher than lithiated graphite. Nonetheless, Li metal anode suffers from poor safety and low cycling efficiency due to its high reactivity. Electrolytes that work with Li anode should possess excellent stability against Li metal or form a highly passivating interface. It is also critical to control the amount of Li in the cell, preferably having no excess Li at the anode side. In this talk next-generation solid state and hybrid electrolytes based on Li-stuffed garnets that enable high-performance Li metal batteries will be discussed.

Metal-Doped ZIF-8 Derived Hollow Carbon for High-Performance Lithium-Sulfur Batteries

Lithium-ion (Li-ion) batteries have been ubiquitously utilized in the modernized world in portable electronic, electrical vehicles, and grid-scale energy storage. However, demand satisfaction for traditional Li-ion batteries is becoming difficult due to their limited capacity and energy density. Moreover, there are challenges related to the availability of non-renewable critical materials for Li-ion batteries such as Co, Ni, and graphite, and environmental pollution during battery creation and recycling. Further neglect of these problems will lead to dramatic consequences at which batteries will become a part of the environmental problems but not a solution to these problems as they should be. Therefore, it is highly imperative to explore novel battery systems that show high energy density, low production cost and low environmental pollution during production, use and recycling. One of the most promising candidates is the lithium-sulphur (LiS) battery, which offers various advantages such as high energy density, high theoretical specific capacity, and affordable cost, because of the high availability of elemental sulphur and carbon used in this type of battery. The theoretical gravimetric energy density of LiS batteries is 2567 Wh/kg which is 4.5 times higher than the energy density of conventional Li-ion batteries. Despite the richness of sulphur in the Earth’s crust and its prominent merits in energy density and cost, several problems have restricted the development of LiS batteries for commercialization. The most notorious and intractable problem is the high solubility of the sulphur species (Li2Sx, 3≤x≤8) in common Li-ion battery electrolytes that leads to the so-called lithium polysulfide (LiPS) shuttle effect and loss of battery capacity, Li metal anode corrosion, and low coulombic efficiency during interaction of the LiPS with Li metal anode. The most prospective solution to address the above drawbacks is sulphur incorporation with a porous, high-conductive carbon host that will tolerate sulphur volume expansion, improve the conductivity of the electrode, prevent the shuttle effect, and allow reversible lithium-ion migration during charging and discharging.However, to achieve the excellent operation performances of the porous carbon host its properties should be carefully tuned and the LiPS absorption ability of the carbon host should be improved for example by metal oxide doping. Many different strategies for the creation of the required material were proposed in recent years. Unfortunately, many proposed synthetic methods require a hard template to provide fine control of the pore distribution in the materials, which is a significant drawback as in this case harsh conditions are required for template removal. In addition, the formation of doped carbons with good electrical conductivity often demands high temperatures, simultaneously causing the undesirable reduction of metal cations to their metallic state followed by the aggregation to form nanoparticles, together with the collapse of the carbon matrices. Therefore, it still urgently needs to find a new strategy to produce a porous carbon host for the sulfur with fine porosity and good lithium polysulfide absorption ability, which purpose to accelerate the successful commercialization of this battery technology on the market.In our current work, we are investigating the possibility to synthesize finely dispersed metal oxide catalysts on hollow N-doped porous carbon capsules produced from zeolitic imidazolate framework (ZIF-8). The coating of the ZIF-8 with metal–tannic acid coordination polymer allows to uniformly dispersed metal oxide nanoparticles, such as Fe2O3, MnO, CoO etc., on hollow carbon capsules after the pyrolysis process. Moreover, the carbon produced by ZIF-8 pyrolysis is expected to be both doped with nitrogen and highly porous, which should have a positive effect on the maximum sulfur loading possibility in the carbon host and lithium polysulfide absorption ability. In addition, the used approach for the synthesis of the hollow N-doped porous carbon allows the distribution of multicomponent metal oxide nanoparticles on the surface of the hollow carbon capsules, which may have a synergetic effect and improve the lithium polysulfide absorption ability of the produced materials. The structural, compositional, and morphological properties of the created material are investigated using SEM, EDS, XPS, Raman spectroscopy, FTIR and TGA techniques. The effect of the different metal oxide nanoparticles and their combinations on the lithium polysulfide absorption ability of the synthesized materials are investigated by analysis of the electrochemical performances of the Li-S batteries, where synthesized material was used as the sulfur host during the creation of the Li-S battery cathode.

Innovative Investigation of Ordered Mesoporous Carbon Modified Separator for High Performance Lithium-Sulfur Batteries

These days, many portable electronic devices are used widely, and it makes secondary batteries important for future innovation. Li-ion battery which is most commonly used has the high specific energy and long cycle life. But it has problems with high price and possibility of explosion. Also it reaches the limitations of energy density for electric vehicles (EVs) and energy storage systems (ESS). Lithium-Sulfur battery is becoming a one of the promising alternatives. It has high theoretical capacity (1,675 mAh g-1) and specific energy density (~2600 Wh kg-1) and low cost. Also it is eco-friendly and safe. However, there is the primary problem to be commercialized. That one is called shuttle effect, which means dissolution of polysulfide into the electrolyte in the repetitive charging and discharging. It makes capacity decrease and internal resistance increase. And the active material and the discharge products, which are sulfur and Li2S2, Li2S, have low conductivity. The irreversible volume expansion during electrochemical reaction reaches to 80%. [1,2] To alleviate these problems, various sulfur host materials and modified separators have been investigated. [3,4] One of the representative approach is to apply carbon materials as sulfur hosts. Sulfur must be dispersed throughout the carbon conductor because of its low intrinsic electrical conductivity. The carbon matrix functions as a network for rapid electron transport. Various carbon materials, such as porous carbons, carbon nanotubes, or carbon materials with heteroatoms or chemical groups such as N, O, and S, have been employed to minimize polysulfide migration. One of the most effective sulfur hosts for limiting polysulfide diffusion is mesoporous carbon. By virtue of their inherent porosity and conductive carbon architecture, mesoporous carbon hosts have demonstrated better cycling performance. Another method for dealing with the shuttle effect is to form an interlayer between the cathode and the separator. Because the separator is an important role in battery safety and electrochemical performance, designing a high quality separator is critical for the development of high performance Li-S batteries. Separators made of polypropylene (PP) or polyethylene (PE) are commercially used and have some physical and electrochemical advantages. However, these separators have drawbacks such as low ionic conductivity and poor electrolyte compatibility. Various materials have been studied and used for modifying materials on the separator. For example, carbon materials, graphene oxides, and metal-organic frameworks are excellent at suppressing the shuttle effect of polysulfide. On the other hand, characterizing these structures and comprehending polysulfide behavior in these systems during electrochemical reaction, remain substantial challenges. Herein, we report on a dual-functional modified separator by applying ordered mesoporous carbon (OMC) on a commercial separator.The mesopores and the micropores of the OMC own a specific physical adsorption capability for polysulfide, thus it can adsorb a large amount of polysulfide. In addition, it is thermally and chemically stable. Also, the OMC can be detected by operando small-angle scattering (SAXS). In recent years, SAXS approach was applied to explain the ordered porous structure of sulfur host materials for Li-S batteries. These research provide information on how sulfur is adsorbed by porous carbon. This analysis identifies the changes of sulfur species as to whether polysulfide is adsorbed in mesopores or solid discharge products are formed on the surface, or infiltrated into micropores. The use of in-depth characterization techniques allows for more precise and independent assessment of the rapid electrochemical reactions in Li-S batteries. In brief, the highly ordered mesoporous carbon was synthesized, and it was used as an interlayer that served not only as a physical barrier to limit the polysulfide shuttle phenomena but also as an additional current collector to reuse active materials. By promoting the electrochemical reaction of active materials, it exhibited better electrochemical performance such as high capacity, stable cycle performance, and improved rate performance. The adsorbed polysufide and the behavior of sulfur species in the OMC during cycling were investigated using operando SAXS to acquire insight into the role of the OMC modified separator.[1] Li, Z.; He, Q.; Xu, X.; Zhao, Y.; Liu, X.; Zhou, C.; Ai, D.; Xia, L.; Mai, L. Adv. Mater. 2018, 30 (45), 1804089.[2] Zeng, L.-C.; Li, W.-H.; Jiang, Y.; Yu, Y. Rare Met. 2017, 36 (5), 339-364.[3] Liu, Z.; Liu, B.; Guo, P.; Shang, X.; Lv, M.; Liu, D.; He, D. Electrochim. Acta 2018, 269, 180-187.[4] Schuster, J.; He, G.; Mandlmeier, B.; Yim, T.; Lee, K. T.; Bein, T.; Nazar, L. F. Angew. Chem. 2012, 124 (15), 3651-3655. Figure 1

Heterointerface-Induced Fast Na+ Transport of Sn Anode Using a Yolk-Shell Structure for Fast-Charging and Stable Sodium-Ion Batteries

Sodium-ion battery (SIB) is a promising next-generation secondary battery system that uses inexpensive sodium resources, which can lower battery production costs. Moreover, based on similar chemical and electrochemical reaction mechanisms as conventional lithium-ion battery (LIB), it is expected that technology development can be rapidly achieved by utilizing existing battery manufacturing processes. However, because of the larger ionic radius (1.02 Å) and weight of sodium compared to those of lithium (0.76 Å), SIBs inevitably have lower energy and power densities compared to LIB. Therefore, to address these challenges, developing suitable host material with superior electrochemical performance (high capacity/high power density/long cyclability) is urgently required.In this regard, metallic Sn has attracted attention as a promising anode material with a high theoretical capacity of 870 mAh/g through the reversible electrochemical (de)alloying reaction with sodium, which could overcome the low energy density limit of hard carbon anode. Nevertheless, due to the interfacial instability of Sn particles upon cycling and the slow alloying reaction rate during the sodiation process, the Sn anode exhibits poor rate performance and insufficient long-term cycling stability. Additionally, the structural degradation caused by significant volume variations further limits its practical implementation in SIBs.Here, to solve the above issues, we propose a hierarchically designed composite anode consisting of Sn yolk and multifunctional C/SiOC shell (denoted as Sn@C/SiOC) via a simple pyrolysis method using the suspension of the Sn precursor in silicone oil. We conducted various physical, chemical, and electrochemical characterization, and we further carried out an in-depth investigation including post-mortem and in-situ EIS analyses to reveal the heterointerface-induced improved sodium-ion storage performance. We expect that the heterointerface modification strategy will contribute to the realization of advanced electrode materials in SIBs and other next-generation energy storage devices.

(Invited) Functional Protective Coatings Based on Polysaccharides and Single-Ion Conducting Polymers for Li Metal Batteries

Li metal batteries are regarded as a promising system to overcome the energy density limitations of the current graphite anode Li-ion batteries, by taking advantage of the low reduction potential of lithium metal (-3.04 V vs SHE) and extremely high theoretical capacity (3860 mAh g-1). However, its use is still plagued with challenges that must be solved in order to achieve a successful Li-metal battery operation, that primarily relies on the performance, stability, and reversibility of the anodic side. Those challenges are related to safety concerns, mainly caused by the uncontrolled growth of high surface area lithium (HSAL) and high volumetric expansion. In this sense, to enable the safe use of Li metal, the concept of protective coating has been proposed, enabling to tailor of adequate interphases that can thermodynamically stabilize the lithium metal surface, and therefore improve the lifespan and safety of the battery. The ideal coating should possess a balance between mechanical strength, flexibility, and ionic conductivity, at the time it enables a uniform and efficient transport of lithium ions. Additionally, it must be electronically insulating and possess high chemical and electrochemically stability. In this context, polymeric coatings can offer good flexibility and elasticity which makes them suitable to adapt to the volumetric changes during lithium stripping/deposition cycles. Moreover, they can form uniform films, creating an ideal contact with lithium metal surface. An attractive group of materials that can provide numerous advantages such as high chemical, mechanical and thermal stability, are polysaccharides, aside from being the highly abundant and renewable resource on the Earth, which can be obtained in different forms.Several studies have shown that concentration polarization during battery operation is the main responsible for HSAL generation and limited cycle life, due to the coupled anion-cation movement in the electrolyte. To solve this problem the use of single-ion conducting polymers (SICPs) can result beneficial due to their immobilized anions to a polymeric backbone, which eases lithium ion transport, boosting lithium transference number (𝑡𝐿𝑖+). In addition, the selection of an appropriate polymeric backbone that can withstand volumetric changes, and allow a satisfactory ionic conductivity is essential. In this regard, the use of cellulose is preferred due to their film formation and mechanical properties, lightweight, high abundance, and biodegradability. Herein, a polymeric coating based on cellulose and P(LiMTFSI) single-ion conductor polymer is studied as a protective coating for metallic Li, in order to prevent HSAL initiation and propagation, as well as to enhance electrochemical stability in liquid and solid polymer electrolyte. The coating effectiveness is tested by casting the solution on activated lithium surface and performing lithium stripping/deposition in Li/Cu pouch cells. Additionally, the correlation with its electrochemical and physicochemical properties is performance based on microscopy and spectroscopy technics, to study the most relevant parameters influencing Coulombic Efficiency.

Poor Cycling Performance of Rechargeable Lithium–Oxygen Batteries Under Lean-Electrolyte and High-Areal-Capacity Conditions: Role of Carbon Electrode Decomposition

There has been considerable interest in developing rechargeable lithium oxygen batteries (LOBs) that have the potential to significantly exceed the energy density limit of a Li ion battery (approximately 300 Wh/kg). Although 500 Wh/kg LOB has been demonstrated and exhibited stable discharge/charge cycle at room temperature condition1, their cyclability remains less than 10 cycle. For realizing the LOB with practically high energy density and long cycle life, the deep understanding of complicated reaction in LOBs has been highly demanded. Especially, the problems specifically associated with the limited electrolyte (“lean-electrolyte”) conditions need to be taken into account in LOBs.Although the importance of investigating negative lithium electrodes in lean-electrolyte systems has been recognised in recent years2,3, specific problems associated with the negative lithium electrode in a LOB has not been investigated so far. In particular, chemical crossover from the positive electrode to the negative electrode is a crucial factor that needs to be taken into consideration. Actually, recent studies have shown that LiOH is formed on the surface of a lithium-metal electrode through reaction with H2O in the electrolyte4,5. This H2O is generated by the decomposition of the tetraethylene glycol dimethyl ether (TEGDME) solvent at the positive oxygen electrode, which then migrates to the negative electrode side to react with the lithium-metal electrode. Consequently, problems related to chemical crossover are prominent in lean-electrolyte LOBs, where the effective water concentration in the electrolyte is much higher than that in an excess electrolyte system.Despite the importance of investigating the reaction of negative lithium electrodes in LOB with appropriate technological parameters, mechanistic details remains unclear due to the technical difficulty for applying non-destructive analytical methods. In the present study, we investigated the reaction of a negative lithium electrode in a lean-electrolyte LOB operating under high areal capacity conditions. The use of advanced non-destructive analytical methods, including three-electrode electrochemical techniques and an in-situ analytical setup revealed that the reaction efficiency of the lithium electrode mostly decreases through chemical crossover from the positive oxygen electrode6. In particular, the H2O generated as a side-product at the positive oxygen electrode crosses over to the negative electrode side and reacts with the lithium-metal electrode to form a porous LiOH/Li2CO3 layer on the electrode surface. LiOH and Li2CO3 accumulates, and the porous layer thickens through repeated discharge/charge cycling, which supresses efficient Li-ion transport through the layer.Furthermore, using a solid-state ceramic-based separator to protect the lithium-metal negative electrode, the side reaction with the negative electrode was considerably suppressed, which helped exclusively assess the degradation phenomena occurring in the oxygen positive electrode. By series of in-situ and ex-situ analysis revealed the following points: (i) Although the electrolyte degradation intensified with increasing repeated discharge/charge cycling, the scarcity of the electrolyte minimally influenced the cycle life of the LOBs. (ii) Most of the Li2CO3-like solid-state side products decomposed during charging at voltages higher than 3.8 V. (iii) Severe decomposition of the carbon electrode occurred during cycling, and an equivalent amount of CO2 was generated during charging at voltages higher than 3.8 V. Because the carbon electrode used in these experiments merely decomposed via simple electrochemical oxidation at voltages up to 4.5 V, the carbon electrode was considered to deteriorate through the decomposition of its solid-state side products. The findings of this study are anticipated to guide future investigations on the advancement of LOBs. In particular, detailed understanding of the reaction at the interface between the carbon electrode and solid-state products is crucial for realizing practical high-energy-density LOBs with long cycle life.

Hydrogen Fuel Cell Integration: Automotive, Residential Power Generation & Portable Devices

Hydrogen fuel has emerged as a promising element in the quest for sustainable energy solutions across diverse sectors. This abstract distils the findings and insights from extensive research into hydrogen fuel integration, focusing on its applications in the automotive industry, residential power generation, and portable devices. In the automotive sector, hydrogen fuel cell vehicles (FCVs) offer a zero-emission alternative with extended driving ranges and rapid refuelling times, addressing some of the limitations of battery electric vehicles (BEVs). However, the successful integration of hydrogen as a transportation fuel hinges on the development of a robust refuelling infrastructure, cost reductions in fuel cell technology, and the optimization of energy-intensive hydrogen production processes. In residential power generation, hydrogen shows promise as a versatile energy carrier, capable of powering homes through fuel cells or combined heat and power (CHP) systems. To ensure sustainable residential hydrogen power, research efforts should continue to focus on efficient hydrogen production methods, such as advanced electrolysis powered by renewable energy sources. Furthermore, the integration of hydrogen in portable devices, including backup power systems and mobile electronics, is being explored. Overcoming challenges related to safe hydrogen storage, efficient energy conversion, and addressing energy density limitations are critical for expanding the utility of hydrogen in this domain. To drive further advancements, key research directions include the development of lightweight and high-capacity hydrogen storage materials, improvements in energy conversion efficiency, and enhanced safety measures for hydrogen-powered portable devices. Moreover, cross-sector collaboration between automotive, residential, and portable device applications is vital to optimize hydrogen production and utilization. Regulatory support and incentives play a pivotal role in promoting the adoption of hydrogen technologies, along with comprehensive life-cycle assessments to quantify their environmental impact.

Constructing molecule-metal relay catalysis over heterophase metallene for high-performance rechargeable zinc-nitrate/ethanol batteries

Zinc-nitrate batteries can integrate energy supply, ammonia electrosynthesis, and sewage disposal into one electrochemical device. However, current zinc-nitrate batteries still severely suffer from the limited energy density and poor rechargeability. Here, we report the synthesis of tetraphenylporphyrin (tpp)-modified heterophase (amorphous/crystalline) rhodium-copper alloy metallenes (RhCu M-tpp). Using RhCu M-tpp as a bifunctional catalyst for nitrate reduction reaction (NO 3 RR) and ethanol oxidation reaction in neutral solution, a highly rechargeable and low-overpotential zinc-nitrate/ethanol battery is successfully constructed, which exhibits outstanding energy density of 117364.6 Wh kg −1 cat , superior rate capability, excellent cycling stability of ~400 cycles, and potential ammonium acetate production. Ex/in situ experimental studies and theoretical calculations reveal that there is a molecule-metal relay catalysis in NO 3 RR over RhCu M-tpp that significantly facilitates the ammonia selectivity and reaction kinetics via a low energy barrier pathway. This work provides an effective design strategy of multifunctional metal-based catalysts toward the high-performance zinc-based hybrid energy systems.

Novel zinc-ion hybrid supercapacitors with enhanced specific capacity by redox-active ions

Zinc-ion hybrid supercapacitors (ZHSCs) have been widely reported for its prominent electrochemical performance, promising safety and low cost. However, the limited energy density has long hindered its application in various fields. Herein, novel redox-active ions enhanced aqueous ZHSCs are proposed, in which VOSO4 served as the additive in electrolytes to promote the specific capacity through redox pairs. In these supercapacitors, redox-active ions (VO2+) were introduced into 1 M ZnSO4 electrolyte and occurred redox reactions during the charge/discharge cycles, which provided additional capacity. Combined with the reversible ion adsorption on the surfaces of activated carbon, the prepared ZHSCs exhibit an ultra-high specific capacity of 9.09 mAh/cm2 at 0.8 mA/cm2, which surprisingly exceeds that of ZHSCs without redox-active ions by about 10 times.

High-Sulfur Loading and Single Ion-Selective Membranes for High-Energy and Durable Decoupled Aqueous Batteries.

The decoupled battery design is promising for breaking the energy density limit of traditional aqueous batteries. However, the complex battery configuration and low-selective separator membranes restrict their energy output and service time. Herein, a zinc-sulfur decoupled aqueous battery is achieved by designing a high-mass loading sulfur electrode and single ion-selective membrane (ISM). A vertically assembled nanosheet network constructed with the assistance of a magnetic field enables facile electron and ion conduction in thick sulfur electrodes, which is conducive to boosting the cell-level energy output. For the tailored ISM, the Na ions anchored on its skeleton effectively prevent the crossover of OH- or Cu2+ , facilitating the transport of Na+ and ensuring structural and mechanical stability. Consequently, the Zn-S aqueous battery achieves a reversible energy density of 3988Wh kgs -1 (by sulfur mass), stable operation over 300 cycles, and an energy density of 53.2 mWh cm-2 . The sulfur-based decoupled system may be of immediate benefit toward safe, reliable, and affordable static energy storage.

Enhanced energy density and fast-charging ability via directional particle configuration

The limited energy density of lithium-ion capacitors poses a significant obstacle to their widespread application, primarily stemming from the inability of the electrodes to simultaneously fulfill both high energy density and rapid charging requirements. Experimental data demonstrate that a directional particle configuration can enhance charging speed while maintaining high-capacity density, but it is rarely discussed. Here, we have developed a particle-level electrochemical model capable of reconstructing an electrode with a directional particle configuration. By employing this method, an investigation was conducted to explore how the spatial morphology characteristics of particle configuration impact the energy storage characteristics of electrodes. Results demonstrate that rational particle configuration can effectively enhance the transport of lithium ions and create additional space for lithium-ion storage. With the same particle size distribution, the best electrode can increase the discharge capacity by up to 132.4% and increase the charging SOC by 11.3% compared to the ordinary electrode under the condition of 6 C. These findings provide a further understanding of the energy storage mechanism inside the anisotropic particle distribution electrode, which is important for developing high-performance lithium-ion capacitors.

Human friendly biodegradable supercapacitors utilizing water-soluble MoOx@Mo-foil as electrode and normal saline as electrolyte

The rapid advancement of biomedical technology has sparked increasing interest in developing biodegradable implantable energy storage devices for applications in biosensors and bioelectronics. However, the limited energy density, biocompatibility, and degradability of existing materials have posed significant challenges to their widespread adoption in the biomedical field. In response, this study presents an electrode material for a solid-state biodegradable supercapacitor consisting of an array structure of molybdenum oxide (MoOx) nanosheets in situ grown on water-soluble molybdenum foil (Mo-foil). The MoOx@Mo-foil electrode exhibits exceptional electrochemical performance, suppressing previous designs. It demonstrated a high capacitance of 433.3 F/g at 1 A/g, and even at 10 A/g, it has a favorable rate capability of 48.9%. Furthermore, cycling stability test revealed an outstanding endurance, with an impressive retention of 88.0% after 5000 cycles. An symmetrical supercapacitor was assembled by combining two MoOx@Mo-foil electrodes with remarkable energy storage capabilities and cycling stability of 94.3% over 5000 cycles. Additionally, the biodegradable supercapacitor exhibited a high energy density of 40.95 Wh/kg at 600.48 W/kg. Moreover, the device is fully biodegradable, which paves the way for advancing the field of bioelectronics and propelling the development of sustainable energy storage technologies for biomedical applications.

Phase field modeling of fatigue crack growth retardation under single cycle overloads

A zone-based crack retardation model that responds to single cycle overloads is applied to a phase field fatigue framework. Fatigue crack growth is incorporated through the degradation of fracture toughness in the phase field fracture model where a representative loading strategy is followed instead of explicit cyclic loading. The model is demonstrated to capture Paris-Erdogan law type behavior. Crack growth retardation following an overload cycle is simulated through a zone ahead of the crack tip taking inspiration from existing plastic zone-based retardation models. The retardation zone is described through a strain energy density limit, with the overload ratio controlling the extent to which the fatigue damage accumulation rate is slowed inside the retardation zone. The model is implemented utilizing user subroutines in Abaqus with coupled-temperature displacement elements where temperature acts as a stand in for the phase field parameter. The model is found capable of reproducing experimental levels of fatigue life gains and reduction in crack growth rate for compact tension and center-cracked tension panel specimens when various overload levels are applied. Furthermore, the model is demonstrated to be able to capture complex crack paths with great accuracy.

Hierarchical Nickel Cobalt Phosphide @ Carbon Nanofibers Composite Microspheres: Ultrahigh Energy Densities of Electrodes for Supercapacitors.

Supercapacitors (SCs) are widely used in energy storage devices due to their superior power density and long cycle lifetime. However, the limited energy densities of SCs hinder their industrial application to a great extent. In this study, we present a new combination of metallic phosphide-carbon composites, synthesized by directly carbonizing (Ni1-xCox)5TiO7 nanowires via thermal chemical vapor deposition (TCVD) technology. The new method uses one-dimensional (1D) (Ni1-xCox)TiO7 nanowires as precursors and supporters for the in situ growth of intertwined porous CNF microspheres. These 1D nanowires undergo microstructure transformation, resulting in the formation of CoNiP nanoparticles, which act as excellent interconnected catalytic nanoparticles for the growth of porous 3D CNF microspheres. Benefiting from the synergistic effect of a unique 1D/3D structure, the agglomeration of nanoparticles can effectively be prevented. The resulting CNF microspheres exhibit an interconnected conductive matrix and provide a large specific surface area with abundant ion/charge transport channels. Consequently, at a scanning rate of 10 mV s-1, its specific capacitance in 1.0 M Na2SO4 + 0.05 M Fe(CN)63-/4- aqueous solution is as high as 311.7 mF cm-2. Furthermore, the CoNiP@CNFs composite film-based symmetrical SCs show an ultrahigh energy density of 20.08 Wh kg-1 at a power density of 7.20 kW kg-1, along with outstanding cycling stability, with 87.2% capacity retention after 10,000 cycles in soluble redox electrolytes. This work provides a new strategy for designing and applying high-performance binary transition metal phosphide/carbon composites for next-generation energy storage devices.

Lithium metal anode: Past, present, and future

AbstractOver the past three decades, lithium‐based batteries have greatly influenced our daily lives. However, their limited energy density poses challenges in meeting growing demand. To increase energy density, lithium metal anode is considered critical. This review systematically examines the history of lithium metal anode development, highlights notable advances in fundamental understandings, materials design, and characterization techniques. Forthcoming opportunities are discussed to promote the practical applications of lithium metal anodes.

Azacyclic Anchor-Enabled Cohesive Graphite Electrodes for Sustainable Anion Storage.

Advanced energy-storage devices are indispensable for expanding electric mobility applications. While anion intercalation-type redox chemistry in graphite cathodes has opened the path to high-energy-density batteries, surpassing the limited energy density of conventional lithium-ion batteries , a significant challenge remains: the large volume expansion of graphite upon anion intercalation. In this study,a novel polymeric binder and cohesive graphite cathode design for dual-ion batteries (DIBs) is presented, which exhibits remarkable stability even under high voltage conditions (>5V). The innovative binder incorporates an acrylate moiety ensuring superior oxidative stability and self-healing features, along with an azide moiety, which allows for azacyclic covalent bonding with graphite and interchain crosslinking. A simple 1-h ultraviolet treatment is sufficient for binder fixation within the electrode, leading to the covalent bond formation with graphite and the creation of a robust three-dimensional network. This modification facilitates deeper and more reversible anion intercalation, leading to improved capacity, extended lifespan, and sustainable anion storage.Thebinder design, exhibiting exceptional adhesive properties and effective stress mitigation, enables the construction of ultrathick graphite cathodes. These findings provide valuable insights for the development of advanced binders, paving the way for high-performance DIBs.

Iron-doped nickel–cobalt bimetallic phosphide nanowire hybrids for solid-state supercapacitors with excellent electromagnetic interference shielding

The development of flexible and wearable electronics subjects to the limited energy density and accompanying electromagnetic pollution. With a high theoretical specific capacity, nickel–cobalt bimetallic phosphide (NiCoP) is considered to be potential cathode materials for supercapacitor. However, the pristine NiCoP fails to display excellent electrochemical performance due to its inferior rate performance and cycling stability. Herein, we design Fe doped NiCoP nanowire arrays on carbon cloth (Fe-NiCoP/CC) as the cathode for supercapacitors. The introduced Fe doping enable to increase in the electronic conductivity and enhance the adsorption of OH−, supported by the density functional theory (DFT) analysis. As a result, Fe-NiCoP/CC electrode displays a high areal capacity of 3.18 F cm−2 at 1 mA cm−2, superb rate capability (86.3 % capacity retention at 20 mA cm−2) and outstanding structure stability, superior to the NiCo/CC, FeNiCo/CC, and NiCoP/CC counterparts. Moreover, the assembled Fe-NiCoP/CC||VN/CNT/CC hybrid supercapacitor (HSC) device delivers a high energy density of 176.9 μWh cm−2 at the power density of 750 μW cm−2. More importantly, the designed electrodes and assembled HSC device exhibits excellent electromagnetic interference (EMI) shielding performance. This design concept presented in this paper can provide insights into the construction of multifunctional and high-performance flexible electronic devices.

Synergising hard-carbon and soft-carbon interactions for delivering metal-free microscale supercapacitors with high specific energy and rapid power delivery

Overcoming the limitations of low energy density and efficiency is a pertinent challenge for the continued development of micro-supercapacitive (MSC) energy storage devices. Traditional metal-thin film-based current collectors suffer from improper interfacial contact with the active material leading to rapid decay in cyclability, while carbon based current collectors underperform in energy density and energy efficiency. In this submission, we design multiscale hierarchical carbon nanostructures and achieve synergistic interactions between them that overcome these limitations. Specifically, the highly conductive (0.2 S/cm) laser-induced-carbon (LIC) acts as an effective current collector with negligible iR drop and simultaneously establishes robust interface with multidimensional nanostructured carbons made-up of (a) porous nanostructured hardcarbon florets (NCF) with high surface area (948 m2/g), open-ended framework and graded porosity and (b) conventional soft-nanocarbons such as one-dimensional single wall carbon nanotubes (CNT) and two-dimensional-graphene (Gr). Consequently, the binder-free MSC resulting from the combination of LIC, NCF and CNT exhibits outstanding high specific capacitance (18 mF/cm2), energy density (10 μWh/cm2), and relaxation time constant (67 ms) without sacrificing power density (1.66 mW/cm2). This is clearly reflected in the unique solitary position achieved by the MSC in the Ragone plot. Fundamentally, the addition of CNT and its integration with non-graphitizable, hard-carbon NCF mimics a ball-net structure that facilitates the ion-migration pathways and thereby delivers the combination of highest energy density and scan rate capability (12,000 mV/s) among all MSCs reported.